MORPHOLOGICAL-STUDIES ON THE LIFE-SPAN, DEVELOPMENTAL STAGES, SENESCENCE AND DEATH OF FRUIT BODIES OF AGARICUS-BISPORUS

In this investigation, we have determined the life span of the fruit b odies of Agaricus bisporus grown in a protected cultivation environmen t as 36 d. We describe the morphological changes occurring in ageing m ushrooms and find that signs of senescence become visible around day 1 8; they steadily increase in amplitude towards the end of the fruit bo dies' life. Cytologically, karyolysis and focal cytoplasmolysis were t he first signs followed by indications of an increased permeability of the cytoplasmic membranes and by structural changes of the cell wall. These changes result in extracellular aggregations of the lyric cell remains encapsulating or bridging the hyphal cells. Cells of the stipe tissues were transformed to empty cylinders or had irregularly collap sed. Most basidia and subhymenial cells remained alive even on day 36. When the mushrooms were cultivated according to our usual growth proc edures, about 50% of the fruit bodies were infected by Trichoderma har zianum and/or Pseudomonas tolaasii on day 18; all fruit bodies died on day 24 due to diffuse bacterial and mycotic infections manifesting th emselves by tissue necrosis and discoloration of the caps and stipes. When none of the fruit bodies was harvested at the time of the first f lush they soon formed a canopy of pilei and their growth ceased. On da y 14, all these fruit bodies showed widespread mixed infections follow ed by a diffuse liquefaction necrosis of all tissues including the hym enium. Post-harvest fruit bodies kept at ambient temperature or at 2 d egrees C at low r.h., or at 20 degrees at high r.h. revealed a diffuse cell wall destruction which was followed by cytoplasmic degeneration in due course. Fruit bodies kept refrigerated had the least gross and cell structural changes during our observation period of 7 d. We concl ude that the morphological changes occurring in post-harvest and in se nescent fruit bodies of Agaricus bisporus are different.